In Reconceiving Spinoza, Samuel Newlands boldly takes up the most radical challenge offered by Spinoza's metaphysics: reconciling extreme ontological parsimony and complete expressive plenitude, monism and plurality, unity and multiplicity. This apparent contradiction permeates Spinoza's ontology as well as his physics, psychological theory, and ethics. How can he proclaim the unicity of substance, while describing an infinity of attributes? How is it possible that the Ethics affirms multiple causal chains, while claiming that God is the immanent cause of everything that exists? How can Spinoza base a theory of human solidarity and interconnection on a principled ethical egoism? Newlands’ intriguing and innovative proposal is to address these diverse issues through a unique solution, which applies the power of the conceptual to heal some of the most damaging fractures of Spinoza's philosophy.

This unified (and unifying) strategy, which is delineated in Chapter 2, entails understanding Spinoza as proposing a complex metaphysical structure, capable of conceptual identification, sensitivity, and variability (48–49). Spinoza's metaphysical system is thus capable of conceiving the same object in multiple, mutually consistent ways that can be opaque to substitution. This opacity is explained by the fact that concepts, for Newlands’ Spinoza, are much more fine-grained than their referents, allowing for differentiations that go beyond mere intensionality, as Chapter 9 will conclude (even when such differentiated descriptions are necessarily co-referring). In this context, for example, Spinoza's attributes are ways of conceiving substance which are opaque to substitution: whether or not God is fundamentally extended, or thinking, depends on how we conceive God. In Newlands’ reconstruction, the hyper-intensionality of Spinoza's conceptual approach allows the same object to be the bearer of apparently incompatible properties. However, this does not imply that these rival – and parallel – conceptions result from a difference in mere mental content. In fact, Newlands steadfastly rejects the equipollence of mental and conceptual. Resting on an attribute-neutral description of conceptual relations, his strategy dispels the ghost of idealism and ‘mentalism’ and claims that conceptual relations constitute the backbone of Spinoza's metaphysics in each of the attributes of substance.

The refusal to identify the mental and conceptual realms parallels another key component of Newlands’ interpretative strategy, which he names ‘Conceptual Dependence Monism’. CSM proposes that it is possible to reduce every dependence relation in Spinoza's metaphysics to the relation of ‘being-conceived-through’. In particular, Newlands offers detailed explanations of how inherence, causation, following-from, and existential dependence would each be reduced to conceptual entailment (65–79) under CSM. With an elegant solution that clearly exemplifies the conceptualist strategy introduced earlier, the multiplicity of relations mentioned by Spinoza collapses on itself. Despite the difficulty of addressing each and every one of the occurrences of these diverse relations in Spinoza's metaphysics, Newlands attempts a comprehensive reduction that takes into account a great variety of texts.

However, the full capacity of Newlands’ conceptualist strategy is revealed in Chapter 4, where he employs his radical reading to argue against our traditional image of Spinoza as a necessitarian. Following the steps of conceptual identification, sensitivity, and variability, the modal status of Spinoza's modes is presented as shifting between necessary and contingent. How can this be? Newlands’ response is to affirm that the modal status of a mode depends on the way it is conceived. Independently of conception, a mode lacks a modal status entirely (101). When a mode is conceived only through its essence, excluding the causes of its existence, then we are attending to a rather ‘narrow concept’ of this mode, which can only entail contingency. When the same mode is considered in a way that broadens that concept, including its relations to all other modes, then its modal status is necessary. Furthermore, Newlands adopts the same strategy to tackle several puzzles concerning the nature of essence and individuality in Spinoza's metaphysics, concluding that – just like its modal status – the individuality of a finite mode shifts depending on its conception, and that it is possible to apply multiple ‘broad concepts’ to one and the same individual. Under this interpretation, individuals are ‘elusive’ sorts of beings. They can shift from being a collection of ‘discrete, autonomous, sovereign, and inviolable individuals’ to being parts of larger beings and – eventually – of an organic and comprehensive universal individual (160).

This original approach to individuality is pivotal for the innovative description of Spinoza's ethics provided by Newlands in Chapters 7 and 8. His starting point is the acknowledgment of Spinoza's fundamental ethical egoism, which leads each mode to strive to preserve and enhance its power of acting. Yet, Newlands argues that finite modes can be motivated to act in solidarity with one another and to minimise conflict through that very egoism, once their individuality is ‘transcended’ and they are reconceived as a broader, more inclusive, individual. This leads to the moral transformation of the finite individual, that can reduce its passivity and causal inadequacy by conceiving itself as less distinct or separated from neighbouring individuals, increasing its inclusive conceiving and reducing externality. Employing his conceptualist strategy, Newlands grants metaphysical grounding to this crucial mechanism of Spinoza's ethics. In a slogan, ‘conceptual shifts pave the path to moral and salvific transformation’ (210). Reconceiving oneself leads, for Newlands’ Spinoza, to transformation and self-acceptance – ultimately, to beatitude.

Newlands successfully offers, in his extensive and detailed analysis, a thorough reconstruction of many apparently familiar concepts, encompassing Spinoza's metaphysics and ethics. The book's energetic prose approaches Spinoza as a colleague in the hallway, uncovering hidden connections in his use of the category of the conceptual. Newlands probes Spinoza's claims through some of the most severe scrutiny that could be dedicated to contemporary analytic metaphysics. He is not afraid to radically reinterpret some of our shared assumptions regarding Spinoza's metaphysics as a result of his analysis. The key theses of the book are unified by the consistent reference to the conceptual as the fundamental category of Spinoza's metaphysics. The centripetal force of this reading is captivating and will surely make Reconceiving Spinoza a reference point for future developments of the current and active debate regarding the interpretation of Spinoza's philosophy.